Persons flying military aircraft are frequently outfitted with a helmet. The typical helmet weighs approximately four pounds and rests directly on the wearer's head via a foam liner. This helmet/head interface has several disadvantages which compromise the safety and effectiveness of flight personnel.
One disadvantage of the typical helmet, is that pressure points develop at those places where the helmet liner rests upon the wearer's head. These pressure points can make the helmet uncomfortable after only limited periods of use. This source of discomfort has human factors consequences which degrade the performance of flight personnel and contribute to fatigue. Flight crew fatigue negatively influences mission effectiveness and safety.
Another disadvantage of the typical helmet is its performance during high g maneuvers of the aircraft. During such maneuvers, the helmet moves relative to the wearer's head. During a positive g force loading, the helmet is pressed down on the wearer's head thus increasing discomfort due to the additional force exerted on the wearer's head at the pressure points. During negative g force loading, the helmet moves away from the head, and an undesirable degree of tension is created on the helmet chin or jaw strap. This tension is uncomfortable for the wearer.
G force loading moves the helmet in relation to the head, such motion of the helmet causing interference with flight crew vision. Typical helmets are fitted with a visor. As the helmet moves relative to the head, the visor shifts position. This movement creates optical errors.
A fourth disadvantage of the typical helmet is lack of ventilation. The helmet often becomes hot and uncomfortable after a period of wear.
A fifth disadvantage of the typical helmet is that the visor or optical elements may become fogged from condensation of the moisture contained in the wearer's breath. A fogged visor or other optical elements also interfere with the wearer's vision and impact safety and effectiveness.